1. Field of the Invention
This invention relates to a polyester backed acrylic composite molded structure. More particularly, it relates to a composite structure having a polyester polymeric backing material applied during a molding process to an acrylic shell for manufacturing of lightweight durable articles such as sanitary fixtures including bathtubs, sinks, shower receptors, lavatories and the like which are lightweight, and resist damage and delamination when subjected to impact, the weight of the user and thermal shock.
2. Background of the Related Art
In the development of bathroom and kitchen fixtures, as well as bathtubs, whirlpool tubs and other composite articles, the traditional porcelain-cast iron fixtures have gradually been replaced by lighter and more resilient composite structures. While porcelain-cast iron and enameled fixtures had the advantage of having a very solid feel and a high weight bearing capability, one disadvantage of these fixtures has been their susceptibility to impact damage and extreme weight which causes great difficulties in moving and installing large fixtures such as sinks, bathtubs and whirlpool tubs.
Initial attempts by the industry to replace these porcelain-cast iron fixtures were unsuccessful. The early composite structures had a plastic, hollow feel which would deform, crack, chip or delaminate when subjected to impact, thermal shock, or the weight of the typical bather. In addition, these composite structures would often delaminate, crack, craze or chip when subjected to impact from the outside of the structure during manufacturing, transportation and installation of the fixture.
A successful solution to these problems is disclosed in U.S. Pat. No. 4,664,982 to Genovese et al., and in U.S. Pat. No. 5,049,443 to Kuszaj et al., the disclosure of both of which are incorporated by reference herein. Both disclose composite enamelled steel or stainless steel fixtures which have the look and feel of the earlier porcelain-cast iron fixtures. The structures are light, have high structural strength, and resist delamination, chipping and denting due to impact or thermal shock. The composite structures are formed from a steel or stainless steel which may be enamelled on one or both of its faces. The excellent physical and mechanical properties are imparted to these shells as a result of the chemical bonding of a plastic layer to a non-finish side of the shell. The preferred plastic layer is an isocyanate-modified thermosetting unsaturated polyester or polyether foam which is introduced into a mold containing the shell by reaction injection molding (RIM), or by reinforced reaction injection molding ("RRIM") processing. The foamed plastic is chemically bonded to the shell by the action of silane, a coupling agent which creates chemical linkages between the metallic groups or the SiOH groups in the enamel and the reinforced foamed plastic to form the laminate. These composite structures possess excellent physical and mechanical properties as a result of the chemical bonding of the reinforced foamed polymeric layer to the enamel steel or stainless steel shell. These disclosures do not relate, however, to the manufacture of a composite structure in which an acrylic layer is bonded to a polymeric or plastic molded structure.
Another solution to these problems was the use of a polymeric, cosmetic surface layer bonded directly to a foamed plastic substrate, described as a cross-linked isocyanate-modified thermosetting unsaturated polyester or polyether resin layer to provide a high impact strength, delamination-resistant structure. These structures and their processes of manufacture are disclosed in U.S. Pat. Nos. 4,844,944 and 4,844,955 both to Graefe et al., the disclosures of which are incorporated by reference herein. Methylmethacrylate and commercially available adhesive Thixon 416, manufactured by Whittaker Corp., West Alexandria, Ohio, which contains a blend of 65% solvents, 35% solids including polyurethane phenolic and epoxy resins, was used as a primer to cross-link and chemically bond the polymeric cosmetic layer to the isocyanate groups in the foamed plastic while plastic is cured. The isocyanate was provided in the foamed plastic to provide a very fast cure of the plastic layer during RIM, or RRIM molding.
However, one of the disadvantages of the reaction molding processes discussed above is that the molding processes are carried out under high pressures and require a large and expensive hydraulic press to keep the mold closed and prevent the escape of the reacting polymeric foam during the molding process. Although these molding procedures result in a very fast cure time, the equipment required, such as the hydraulic mold press is expensive, requiring a high capital investment.
Accordingly, it is desirable to provide an improved polymeric composite molded structure and a method of producing same.